From 5c490c51edd5a8e3953fcc439d46c0e138294073 Mon Sep 17 00:00:00 2001
From: Amadeus Demarzi <amadeus@users.noreply.github.com>
Date: Wed, 17 Dec 2025 05:33:46 -0800
Subject: Diffs Performance Improvements (#5653)

Co-authored-by: Adam <2363879+adamdotdevin@users.noreply.github.com>
---
 packages/ui/package.json                      |  1 +
 packages/ui/src/components/diff-ssr.tsx       | 23 ++++++++++-------
 packages/ui/src/components/diff.css           |  2 ++
 packages/ui/src/components/session-review.css |  1 +
 packages/ui/src/context/worker-pool.tsx       | 10 ++++++++
 packages/ui/src/custom-elements.d.ts          |  5 +++-
 packages/ui/src/pierre/worker.ts              | 36 ++++++++++++++++-----------
 7 files changed, 54 insertions(+), 24 deletions(-)
 create mode 100644 packages/ui/src/context/worker-pool.tsx

(limited to 'packages/ui')

diff --git a/packages/ui/package.json b/packages/ui/package.json
index b2e7e331d..618dbf1f0 100644
--- a/packages/ui/package.json
+++ b/packages/ui/package.json
@@ -5,6 +5,7 @@
   "exports": {
     "./*": "./src/components/*.tsx",
     "./pierre": "./src/pierre/index.ts",
+    "./pierre/*": "./src/pierre/*.ts",
     "./hooks": "./src/hooks/index.ts",
     "./context": "./src/context/index.ts",
     "./context/*": "./src/context/*.tsx",
diff --git a/packages/ui/src/components/diff-ssr.tsx b/packages/ui/src/components/diff-ssr.tsx
index b38b4a34f..e367a4fbe 100644
--- a/packages/ui/src/components/diff-ssr.tsx
+++ b/packages/ui/src/components/diff-ssr.tsx
@@ -1,8 +1,9 @@
-import { FileDiff } from "@pierre/diffs"
+import { DIFFS_TAG_NAME, FileDiff } from "@pierre/diffs"
 import { PreloadMultiFileDiffResult } from "@pierre/diffs/ssr"
 import { onCleanup, onMount, Show, splitProps } from "solid-js"
-import { isServer } from "solid-js/web"
+import { Dynamic, isServer } from "solid-js/web"
 import { createDefaultOptions, styleVariables, type DiffProps } from "../pierre"
+import { useWorkerPool } from "../context/worker-pool"
 
 export type SSRDiffProps<T = {}> = DiffProps<T> & {
   preloadedDiff: PreloadMultiFileDiffResult<T>
@@ -12,17 +13,21 @@ export function Diff<T>(props: SSRDiffProps<T>) {
   let container!: HTMLDivElement
   let fileDiffRef!: HTMLElement
   const [local, others] = splitProps(props, ["before", "after", "class", "classList", "annotations"])
+  const workerPool = useWorkerPool()
 
   let fileDiffInstance: FileDiff<T> | undefined
   const cleanupFunctions: Array<() => void> = []
 
   onMount(() => {
     if (isServer || !props.preloadedDiff) return
-    fileDiffInstance = new FileDiff<T>({
-      ...createDefaultOptions(props.diffStyle),
-      ...others,
-      ...props.preloadedDiff,
-    })
+    fileDiffInstance = new FileDiff<T>(
+      {
+        ...createDefaultOptions(props.diffStyle),
+        ...others,
+        ...props.preloadedDiff,
+      },
+      workerPool,
+    )
     // @ts-expect-error - fileContainer is private but needed for SSR hydration
     fileDiffInstance.fileContainer = fileDiffRef
     fileDiffInstance.hydrate({
@@ -65,11 +70,11 @@ export function Diff<T>(props: SSRDiffProps<T>) {
 
   return (
     <div data-component="diff" style={styleVariables} ref={container}>
-      <diffs-container ref={fileDiffRef} id="ssr-diff">
+      <Dynamic component={DIFFS_TAG_NAME} ref={fileDiffRef} id="ssr-diff">
         <Show when={isServer}>
           <template shadowrootmode="open" innerHTML={props.preloadedDiff.prerenderedHTML} />
         </Show>
-      </diffs-container>
+      </Dynamic>
     </div>
   )
 }
diff --git a/packages/ui/src/components/diff.css b/packages/ui/src/components/diff.css
index 345271a12..3251eb4c6 100644
--- a/packages/ui/src/components/diff.css
+++ b/packages/ui/src/components/diff.css
@@ -1,4 +1,6 @@
 [data-component="diff"] {
+  contain: content;
+
   [data-slot="diff-hunk-separator-line-number"] {
     position: sticky;
     left: 0;
diff --git a/packages/ui/src/components/session-review.css b/packages/ui/src/components/session-review.css
index 0cd228592..35df4a80f 100644
--- a/packages/ui/src/components/session-review.css
+++ b/packages/ui/src/components/session-review.css
@@ -5,6 +5,7 @@
   height: 100%;
   overflow-y: auto;
   scrollbar-width: none;
+  contain: strict;
   &::-webkit-scrollbar {
     display: none;
   }
diff --git a/packages/ui/src/context/worker-pool.tsx b/packages/ui/src/context/worker-pool.tsx
new file mode 100644
index 000000000..fc2eecc03
--- /dev/null
+++ b/packages/ui/src/context/worker-pool.tsx
@@ -0,0 +1,10 @@
+import type { WorkerPoolManager } from "@pierre/diffs/worker"
+import { createSimpleContext } from "./helper"
+
+const ctx = createSimpleContext<WorkerPoolManager | undefined, { pool: WorkerPoolManager | undefined }>({
+  name: "WorkerPool",
+  init: (props) => props.pool,
+})
+
+export const WorkerPoolProvider = ctx.provider
+export const useWorkerPool = ctx.use
diff --git a/packages/ui/src/custom-elements.d.ts b/packages/ui/src/custom-elements.d.ts
index b756e51da..49ec4449f 100644
--- a/packages/ui/src/custom-elements.d.ts
+++ b/packages/ui/src/custom-elements.d.ts
@@ -1,12 +1,15 @@
+import { DIFFS_TAG_NAME } from "@pierre/diffs"
+
 /**
  * TypeScript declaration for the <diffs-container> custom element.
  * This tells TypeScript that <diffs-container> is a valid JSX element in SolidJS.
  * Required for using the @pierre/diffs web component in .tsx files.
  */
+
 declare module "solid-js" {
   namespace JSX {
     interface IntrinsicElements {
-      "diffs-container": HTMLAttributes<HTMLElement>
+      [DIFFS_TAG_NAME]: HTMLAttributes<HTMLElement>
     }
   }
 }
diff --git a/packages/ui/src/pierre/worker.ts b/packages/ui/src/pierre/worker.ts
index e47268d4e..2d2640674 100644
--- a/packages/ui/src/pierre/worker.ts
+++ b/packages/ui/src/pierre/worker.ts
@@ -1,20 +1,28 @@
-import { getOrCreateWorkerPoolSingleton } from "@pierre/diffs/worker"
+import { getOrCreateWorkerPoolSingleton, WorkerPoolManager } from "@pierre/diffs/worker"
 import ShikiWorkerUrl from "@pierre/diffs/worker/worker.js?worker&url"
 
 export function workerFactory(): Worker {
   return new Worker(ShikiWorkerUrl, { type: "module" })
 }
 
-export const workerPool = getOrCreateWorkerPoolSingleton({
-  poolOptions: {
-    workerFactory,
-    // poolSize defaults to 8. More workers = more parallelism but
-    // also more memory. Too many can actually slow things down.
-    // poolSize: 8,
-  },
-  highlighterOptions: {
-    theme: "OpenCode",
-    // Optionally preload languages to avoid lazy-loading delays
-    // langs: ["typescript", "javascript", "css", "html"],
-  },
-})
+export const workerPool: WorkerPoolManager | undefined = (() => {
+  if (typeof window === "undefined") {
+    return undefined
+  }
+  return getOrCreateWorkerPoolSingleton({
+    poolOptions: {
+      workerFactory,
+      // poolSize defaults to 8. More workers = more parallelism but
+      // also more memory. Too many can actually slow things down.
+      // NOTE: 2 is probably better for OpenCode, as I think 8 might be
+      // a bit overkill, especially because Safari has a significantly slower
+      // boot up time for workers
+      poolSize: 2,
+    },
+    highlighterOptions: {
+      theme: "OpenCode",
+      // Optionally preload languages to avoid lazy-loading delays
+      // langs: ["typescript", "javascript", "css", "html"],
+    },
+  })
+})()
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